Copper has many important uses in the form of wire, sheet, etc. as a result of its desirable electrical and heat conducting properties. However, pure copper has relatively weak tensile strength. Prior art workers have sought to overcome this deficiency by forming what has been referred to as an "in-situ" composite of Cu and X where X is Nb, Ta, W or other refractory metal. The composite so formed includes elongated strengthening filaments of the X constituent dispersed in a Cu matrix constituent.
"In-situ" Cu-X composites have been produced by a solidification/reduction process wherein a Cu-X melt is cast and solidified to provide a two phase body (e.g., an ingot having X dendrites in a Cu matrix) that is then mechanically reduced (e.g., by swaging, rolling, drawing, etc.) to form the composite. "In-situ" composites have also been produced by a powder compaction/reduction process wherein a mixture of Cu and X powders is initially compacted to densify the particulate mixture and then mechanically reduced to form the composite. The composites produced in these ways are quite ductile and can be mechanically reduced to very large strains without breakage. The mechanical reduction operation converts the X (refractory metal) dendrites or particles, as the case may be, into the strengthening filaments which serve to reinforce and greatly increase the strength of the composite.
Prior art workers have been successful in making Cu-Nb, Cu-Ta and other Cu-X composites using the solidification/reduction process as a result of the quite low solubility of the refractory metal in Cu in the liquid state. However, "in-situ" Cu-Fe composites cannot be produced by the solidification/reduction process with satisfactory electrical and heat conducting properties because the Fe is not sufficiently insoluble in liquid Cu.
One prior art worker has suggested that "in-situ" composites of Cu-Fe as well as Cu-Nb and Cu-V can be made using the solidification/reduction process (e.g., see Bevk et al., "In Situ Composites IV", pp. 121-133, (1982), ed. Lempke, et al., Elsevier Sci. Pub. Co.). However, as mentioned hereinabove, "in-situ" Cu-Fe composites having acceptable electrical and heat conducting properties cannot be made using the solidification/reduction process as a result of the insufficient insolubility of Fe in solid Cu. Furthermore, the present inventors have discovered that the powder compaction/reduction process is not straightforwardly applicable to the production of "in-situ" Cu-Fe composites and, as heretofore practiced, does not provide a viable method for making high strength, high conductivity Cu-F composites.
Since Cu-Fe composites will enjoy a significant cost advantage over the corresponding Cu-X composites as a result of the low cost of Fe compared to the refractory metals, there is a continuing desire to provide "in-situ" high strength, high conductivity Cu-Fe composites and a viable process for making such composites. The present invention has as an object to satisfy this desire.